The invention relates to a video/audio signal recording and reproducing apparatus and its method in which when video/audio signals recorded on a recording medium are reproduced, even if a double-speed reproduction is performed, all of the audio signals can be read out from the recording medium.
There are many cases where a telephone call suddenly rings or someone suddenly comes while the user is enjoying a television broadcasting program, so that he overlooks a broadcasting program. If the user overlooked a television broadcasting, this program can never be seen except for a program that is rebroadcasted. It is a rare case that the program is rebroadcasted in a short period of time. A news program and a sports program are not rebroadcasted in most cases. In many cases, therefore, if the user overlooked a television broadcasting program, this program cannot be seen forever.
There is a case where a scene such as good scene of a movie or a drama, interview of an important person, highlight scene of a sports program, or the like which the user wants to preserve suddenly starts during the watching of a broadcasting program. In such a case, even if the user immediately sets a VTR, he misses such a scene and he often cannot record the scene.
Therefore, a television receiver such that while the user is watching a broadcasting-program, such a program is always recorded on a recording medium is considered. In such a television receiver, even if there is a sudden telephone call or someone suddenly comes, such a program can be traced back and reproduced and he does not overlook the program. Such a program can be easily preserved and even if a program which the user wants to record suddenly starts, it is possible to cope with it.
As a recording medium in the television receiver such that a program is always recorded onto a recording medium as mentioned above, a hard disk drive can be used. Hitherto, as a recording medium for recording a video signal, a magnetic tape is widely used. However, an accessing speed of the magnetic tape is slow and it is difficult to use it as a recording medium that is used in such a television receiver. Although the use of a semiconductor memory is considered, the semiconductor memory of a large capacity is very expensive. In the semiconductor memory, if a power source is turned off, the preserved program is erased, so that it is inconvenient in case of preserving a program for a long time. On the other hand, in the hard disk drive, a capacity is large and an accessing speed is also high enough.
FIG. 6 shows an example of a construction of a video/audio recording and reproducing apparatus which is used in a television receiver such that a program is always recorded on a recording medium. For example, a video signal obtained on the basis of a received television broadcasting (real-time broadcasting) radio wave is supplied to a terminal 200. An audio signal is supplied to a terminal 201. The video signal supplied to the terminal 200 is converted into a digital signal by an A/D converting circuit 202 and is subjected to a decimation, a compression encoding, and the like in a video compressing circuit 203. In this example, a decimation ratio is set to 1/4. Video data outputted from the video compressing circuit 203 is temporarily stored in a buffer memory 204.
Similarly, the audio signal supplied to the terminal 201 is converted into a digital signal by an A/D converting circuit 208 and is compressed and encoded by an audio compressing circuit 209. A decimation on a field unit basis is not performed to the audio signal. Audio data outputted from the audio compressing circuit 209 is temporarily stored into a buffer memory 210.
On the basis of a control of a recording/reproduction controller 207, the video data and audio data temporarily stored in the buffer memories 204 and 210 are read out and are written into a hard disk drive 206 through a bus 205.
The video data and audio data written into the hard disk drive 206 are read out on the basis of the control of the recording/reproduction controller 207. The video data is temporarily stored into a buffer memory 211 and the audio data is temporarily stored into a buffer memory 216.
The compression and encoding of the video data read out from the buffer memory 211 is released by a video decompressing circuit 212 and the resultant video data is converted into an analog signal by a D/A converting circuit 213. The video signal outputted from the D/A converting circuit 213 is supplied to a terminal 214A of a switching circuit 214. Similarly, the compression and encoding of the audio data read out from the buffer memory 216 are released by an audio decompressing circuit 217 and the resultant audio data is converted into an analog signal by a D/A converting circuit 218. The audio signal outputted from the D/A converting circuit 218 is supplied to a terminal 219A of a switching circuit 219.
The video signal is supplied from the input terminal 200 to a terminal 214B of the switching circuit 214. The audio signal is supplied from the input terminal 201 to a terminal 219B of the switching circuit 219. The switching operations of the switching circuits 214 and 219 are controlled by the recording/reproduction controller 207. The signals by the real-time broadcasting supplied from the input terminals 200 and 201 and the reproduction signal read out from the hard disk drive 206 are selectively switched. Outputs of the switching circuits 214 and 219 are led to output terminals 215 and 220 and are reproduced by a CRT monitor apparatus and a speaker, respectively.
The writing operation of the data to the hard disk drive 206 is executed on a unit basis of one set of data in which the video data of one field and the audio data corresponding to four continuous fields in which the video data is set to the head are combined. FIG. 7 shows an example of one set of data comprising the audio data and the video data. The audio data of four continuous fields is stored to the head and, after that, the corresponding video data of one field is stored. The data of each set is time-sequentially continuously arranged for addresses in the hard disk drive 206, respectively.
The writing and reading operations of the data to/from the hard disk drive 206 are executed as follows. FIG. 8 shows an example of a disk accessing method in a one-time speed reproducing mode. As shown in FIGS. 8A and 8B, the video and audio signals are supplied to the terminals 200 and 201, respectively. Each delimiter corresponds to one field. The supplied video and audio signals are converted into the video data and audio data through the foregoing predetermined processes. The video data is written into the buffer memory 204 and the audio data is written into the buffer memory 210.
When time corresponding to four fields of signals a0 to a3 elapses, as shown in an example in FIG. 8C, the audio data (collectively, referred to as audio data e0) obtained by compressing and encoding audio signals b0 to b3 corresponding to first four fields of the input audio signal is written into a predetermined area on the disk 206. Video data a0 based on first one field in a period of time of the signals a0 to a3 of the corresponding input video signal of four fields is written into a subsequent address. Consequently, one set of data comprising the audio data and the video data is written.
Similarly, the writing of the next one set of data is performed with the elapse of time of four fields of signals a4 to a7. In this example, the writing of the next one set of data is executed subsequently to the address of the video data a0.
In the case where the terminals 214B and 219B are selected by the switching circuits 214 and 219, respectively, only the video and audio signals by the real-time broadcasting are transferred to the output terminals 215 and 220 and are reproduced by the monitor apparatus and speaker, respectively. In a monitor output of FIG. 8G, the video signals a0 to a6 and corresponding audio signals b0 to b6 correspond to them.
The reading operation of the data from the hard disk drive 206 will now be described. First, a case of the one-time speed reproduction, namely, the reproduction at a normal speed will now be described. When the one-time speed reproduction is designated, the reading operation of the data from the hard disk drive 206 is started. It is now assumed that the reproduction from a time point that was traced back by only predetermined time t0 is designated. On the addresses in the hard disk drive 206, the address in which the corresponding data has been written is accessed.
The terminals 214B and 219B are selected in the switching circuits 214 and 219 at first, respectively.
When reading out from the hard disk drive 206, time that is required for the disk access is considered. In this example, as shown in FIG. 8D, time t is provided between the writing operation and the reading operation. The time t in the writing operation and the time t in the reading operation don""t need to be equal to each other. First, the audio data is read out and written into the buffer memory 216. Subsequently, the video data is read out and written into the buffer memory 211.
For example, in the example shown in FIG. 8D, first, audio data f0 is read out and written into the buffer memory 216. Subsequently, video data c0 is read out and written into the buffer memory 211. Synchronously with the next field in which the writing has been finished, the data is read out from the buffer memories 211 and 216.
The video data c0 read out from the buffer memory 211 is supplied to the video decompressing circuit 212 and the compression and encoding are released in a real-time manner, so that the video data is decompressed. The reading and decompression of the video data c0 from the buffer memory 211 are repetitively executed every field for a period of time of four fields. Thus, for instance, as shown in FIG. 8E, the video data c0 as much as four fields is repeated and, subsequently, video data c4 as much as four fields is repeated. The decompressed video data c0 is converted into an analog video signal through the D/A converting circuit 213 and is supplied to the input terminal 214A of the switching circuit 214.
The reading operation of the audio data f0 from the buffer memory 216 is performed synchronously with the reading of the video signal. The audio data f0 read out from the buffer memory 216 is supplied to the audio decompressing circuit 217 and the compression and encoding are released in a real-time manner, so that the audio data is decompressed. Thus, as shown in FIG. 8F, the continuous audio data is obtained every field. The decompressed audio data f0 (audio data d0 to d3) is converted into an analog audio signal through the D/A converting circuit 218 and is supplied to the input terminal 219A of the switching circuit 219.
Synchronously with the start of the decompressing operation of the video decompressing circuit 212 or audio decompressing circuit 217, on the basis of the control of the recording/reproduction controller 207, the terminals 214A and 219A are selected in the switching circuits 214 and 219, respectively. Thus, in place of the video signal and audio signal by the real-time broadcasting which were supplied from the input terminals 200 and 201 to the terminals 214B and 219B of the switching circuits 214 and 219, the video signal and audio signal which had already been written and recorded to the hard disk drive 206 in the past are transferred to the output terminals 215 and 220 (FIG. 8G).
The writing and reading operations to/from the hard disk drive 206 as mentioned above are alternately performed. That is, at a time point when the time corresponding to four fields elapses from the start of the previous writing (audio data e0 and video data a0), the reading of the audio data f0 and video data c0 mentioned above has already been finished. Therefore, the writing of the next data (audio data e4 and video data a4) supplied from the input terminals 200 and 201 is executed by processes similar to those mentioned above. When the writing is finished, the next data (audio data f4 and video data c4) is read out after waiting for time t.
FIG. 9 conceptually shows the data recorded in the hard disk drive 206 as mentioned above. In the data, one set is constructed by the audio data of four fields and the video data of one field, and this set is time-sequentially written (FIG. 9A). In the reading of the data, for example, in case of the foregoing one-time speed reproduction, as shown in FIG. 9B in accordance with the order of A, B, C, . . . , the data is time-sequentially read out every set of the audio and video data.
In such a data arrangement, if the writing and reading operations of the data are executed in parallel as mentioned above, there is a case where the address of the data which is read out and was recorded in the past and the address in which new data is written are away from each other. For instance, there is a possibility such that those addresses are away to the inner rim and outer rim of the disk. In such a case, every transition from the writing to the reading or every transition from the reading to the writing, seeking time and rotation waiting time of the disk are necessary. The foregoing time t provided between the writing and the reading is provided to assure the seeking time and rotation waiting time of the disk.
The double-speed reproduction will now be described. FIG. 10 shows an example of a disk accessing method in the double-speed reproduction. It will be obviously understood that even in case of the double-speed reproduction, since the writing of the data into the hard disk drive 206 is executed substantially in the same manner as that in case of the one-time speed reproduction mentioned above as shown in FIG. 10C, its description is omitted here. The supply of the input video signal and the input audio signal is, also executed in a manner similar to the case of the one-time speed reproduction as shown in FIGS. 10A and 10B.
In case of the double-speed reproduction, the data is read out from the hard disk drive 206 every other set of data comprising the audio data as much as four fields and the video data as much as one field. That is, as shown in an example of FIG. 10D, when one set of data comprising the audio data f0 and video data c0 is read out, one set comprising the audio data f4 and video data c4 that is time-sequentially located at the next position is jumped over and another set comprising audio data f8 and video data c8 locating at the next position is read out. In the example of FIG. 9, as shown in FIG. 9C, the sets of data are sequentially read out every other set in accordance with the order of A, B, and C.
Outputs based on the data read out every other set are shown in FIGS. 10E and 10F. As shown in FIG. 10E, in an output video image, the data c0 of one field is repeated by an amount corresponding to four fields. Subsequently, the data c8 is repeated by an amount corresponding to four fields. Thus, the double-speed reproduction is realized.
However, as for an output sound, as shown in FIG. 10F, after the data d0 to d3 as much as four fields was continuously outputted, data d8 to d11 is subsequently outputted. That is, after the data d3, the data d8 locating at the position which is ahead by a distance of four fields is outputted. Therefore, the continuity of the audio signal is not held in the portion of one set of data which was jumped over. There is, consequently, a problem such that the sound has to be erased for a period of time during which the double-speed reproduction is executed.
It is, therefore, an object of the invention to provide a video/audio signal recording and reproducing apparatus and its method in which, for example, when audio and video signals by a real-time broadcasting are always recorded to a recording medium and the recorded signal is read out and reproduced in parallel with the recording, even if a double-speed reproduction is executed, a continuity of an output sound can be held.
To solve the above problem, according to the invention, there is provided a video/audio recording and reproducing apparatus comprising:
a recording medium for recording an audio signal and a video signal; and
recording medium control means for controlling so as to execute the recording to the recording medium and a reproduction from the recording medium in parallel,
wherein the recording medium control means further controls in a manner such that the audio signal and video signal in a predetermined period of time are recorded as one set, one set of audio signal and video signal is reproduced every (nxe2x88x921) sets, and the audio signal in a predetermined period of time subsequent to the audio signal which is reproduced is also reproduced.
According to the invention, there is also provided a video/audio recording and reproducing method comprising:
a step of recording an audio signal and a video signal to a recording medium; and
a recording medium control step of controlling so as to execute the recording to the recording medium and a reproduction from the recording medium in parallel,
wherein in the recording medium control step, there is further executed a control in a manner such that the audio signal and video signal in a predetermined period of time are recorded as one set, one set of audio signal and video signal is reproduced every (nxe2x88x921) sets, and the audio signal in a predetermined period of time subsequent to the audio signal which is reproduced is also reproduced.
As mentioned above, according to the invention, upon reproduction, the video signal in a predetermined period of time is reproduced every (nxe2x88x921) signals and, as for the audio signal, both of the audio signal which is reproduced in correspondence to the video signal which is read out and the audio signal in a predetermined period of time subsequent to the reproduced audio signal are reproduced. Thus, an n-times speed reproduction can be performed without interrupting the sound.